Calculus III - Test #3: Differentials, Gradients, Tangent Planes, and Extreme Values, Exams of Mathematics

A calculus exam focusing on topics such as differentials, gradients, tangent planes, and extreme values. It includes various problems involving differentiating equations, finding gradients and relative directions, determining tangent planes and normal lines, and identifying critical points and extreme values. Students are required to show their work and simplify where necessary.

Typology: Exams

Pre 2010

Uploaded on 08/16/2009

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Calculus III - Test # 3
Professor Broughton March, 2003
Name: Box #
Instructions
Answer all the questions directly on the test.
This is a paper and pencil only exam
Show all the necessary work, and where required, write your answers out
neatly in English sentences.
Make reasonable simpliÞcations.
Question Possible Points Points Obtained
125
225
325
425
Tota l 100
pf3
pf4
pf5

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Calculus III - Test # 3

Professor Broughton March, 2003

Name: Box #

Instructions

ï Answer all the questions directly on the test.

ï This is a paper and pencil only exam

ï Show all the necessary work, and where required, write your answers out neatly in English sentences.

ï Make reasonable simplifications.

Question Possible Points Points Obtained 1 25 2 25 3 25 4 25 Total 100

1. Differentials

  1. Two resistors R 1 and R 2 have a combined resistance in parallel given by:

1 R

R 1

R 2

1.a By differentiating both side of the equation above show that

1 R^2

∂R

∂R 1

R^21

1.b By using equation 1.1 and its for R 2 above find a formula for dR in terms of R 1 , R 2 , dR 1 , dR 2

dR =

1.c Suppose that R 1 and R 2 1. 0000 ◊ 105 and 2. 0000 ◊ 105 so that the computed value of R is ohms 0. 6667 ◊ 105 ≈ 23 ◊ 105. Suppose that the maximum error of both R 1 and R 2 is 100 ohms. Using differentials, estimate the maximum error of the computed value of R.

3. Tangent planes and normal lines

3.a Consider the quadratic surface Q 1 given by:

x^2 − xy + y^2 − yz + z^2 + x + y + z = 6

What is the equation of the tangent plane to the surface at P 0 = (1, − 1 , 1)?

3.b Consider the sphere centered at the origin radius

3 , which also passes through the point P 0. What is the angle between the normal lines to the two surfaces at P 0?

3.c Are the two surfaces orthogonal or tangent? Justify your answer.

4. Critical points and extreme values

  1. Consider f (x, y) = xy(2 − x − y) for 0 ≤ x ≤ 1 , 0 ≤ y ≤ 1. The contour plot appears below

4.a Find all the critical points the given domain.